Ethanol and higher carbon alcohols are utilized as additives in fuel or as feedstocks in the production of other chemical end products. However, the production of alcohols such as ethanol on an industrial scale typically utilizes fermentation processes that require significant amounts of plant feedstock.
In an attempt to reduce the amount of plant feedstock required, the Department of Energy has directed research in the development of liquids from low-cost feedstocks such as biomass and coal in their research laboratories. In 2003, the National Renewable Energy Laboratory (NREL) commissioned a report on the production of ethanol and mixed alcohols via gasification of cellulosic biomass. Studies similar to that described in the NREL report have also been conducted by the Pacific Northwest National Laboratory (PNNL), which has focused its research on the use of biomass in the production of various end products such as transportation fuels and energy production.
Although WIPO pat. publ. no. 2005/021421 to Pearson Technologies, Inc. (publ. March 2005) and U.S. pat. publ. no. 2007/0010589 to Pearson (pub. January 2007) discuss the conversion of syngas into mixed alcohols, these applications are narrowly focused on the use of different catalysts for their specific processes. These and all other extrinsic materials discussed herein are incorporated by reference in their entirety. Where a definition or use of a term in an incorporated reference is inconsistent or contrary to the definition of that term provided herein, the definition of that term provided herein applies and the definition of that term in the reference does not apply.
U.S. Pat. No. 7,781,490 to Lattner, et al. discusses the formation of crude methanol for production of olefins. However, Lattner fails to contemplate processes to produce ethanol and higher-order alcohols. U.S. pat. publ. no. 2010/0069514 to Gracey et al. (publ. March 2010) utilizes a standard reformer and then auto-reformer to convert feedstock into syngas. However, such process is limited to the use of natural gas (methane) as a feedstock.
While U.S. pat. publ. no. 2010/0175320 to Schuetzle et al. (publ. July 2010) devises a system optimized to produce fuel gases such as methane, such system fails to appreciate the use of a methanol recycle loop to increase the yield of higher-order alcohols.
U.S. pat. publ. no. 2009/0048354 to Bell, et al. (publ. February 2009) goes a step further and discusses a system having a methanol generation step that recycles gases back to the very beginning of the process. However, Bell fails to contemplate the use of a CO2 removal unit upstream of the reactor.
Thus, there is still a need for systems and methods for producing higher alcohols from synthesis gas produced from carbonaceous materials and having a methanol recycle loop.